It is known to convert kinetic energy into stored electrical energy during a period of time in which a vehicle is slowing down and such systems are sometimes referred to as a regenerative braking system or an energy recuperation system. However, there is increasing pressure on the manufacturers of motor vehicles to reduce fuel consumption.
The inventors herein have recognized issues with such approaches and have recognized an opportunity to further reduce fuel consumption while also potentially reducing exhaust emissions by constructing and using a fuel supply system of a motor vehicle in the manner described herein. For example, the fuel usage of a motor vehicle can be reduced by using a fuel supply system configured to provide a method of recuperating energy from the motor vehicle. In one particular example, the method comprises during a vehicle over-run event wherein substantially no fuel is supplied to an engine, operating a high pressure fuel pump at a high demand level to store fuel in an accumulator, the high pressure fuel pump being engine driven and operable at least at high and low demand levels, and the accumulator being selectively connectable to the high pressure fuel pump and the engine, such that it is connected during some conditions, and not connected during other conditions.
Therefore, according to a first aspect of the present disclosure there is provided a method of recuperating energy from a motor vehicle using a fuel supply system of an engine of the motor vehicle, the fuel supply system including an engine driven high pressure fuel pump operable at least at high and low demand levels and a high pressure fuel accumulator selectively connectable to the high pressure fuel pump and the engine wherein the method comprises, during a vehicle over-run event in which substantially no fuel is being supplied to the engine, operating the high pressure fuel pump at the high demand level and storing fuel from the high pressure fuel pump in the accumulator. As one example, the high demand level is a maximum demand level of the high pressure fuel pump. In this way, the technical result is achieved that allows for further reduction in fuel usage of the motor vehicle.
The method further comprises supplying fuel from the accumulator to the engine during a subsequent engine fuel demand event and operating the high pressure fuel pump at the low demand level during the period in which fuel is being supplied from the accumulator to the engine. The subsequent engine fuel demand event may be an event in which fuel is required by the engine to accelerate the motor vehicle. As one example, the low demand level may be a minimum demand level of the high pressure fuel pump.
The method may further comprise, during the vehicle over-run event, reducing the demand level for the high pressure fuel pump from the high demand level to the low demand level if the accumulator is full. Further still, the method may comprise, during the vehicle over-run event, operating the high pressure fuel pump at the high demand level if the speed of the motor vehicle is above a predefined minimum vehicle speed and operating the high pressure fuel pump at the low demand level if the speed of the motor vehicle is below the predefined minimum vehicle speed.
According to a second aspect of the present disclosure there is provided a fuel supply system of an engine of a motor vehicle comprising a fuel reservoir, a low pressure fuel pump to supply fuel from the reservoir to an engine driven variable output high pressure fuel pump operable at least at high and low demand levels, at least one fuel injector to supply fuel at high pressure to the engine, a fuel accumulator to store fuel at high pressure, a valve means to control the flow of fuel between the high pressure fuel pump, the accumulator and the engine and an electronic controller to control the operation of the high pressure fuel pump, the valve means and the at least one fuel injector, wherein the electronic controller is operable during a vehicle over-run event in which substantially no fuel is being supplied to the engine, to operate the high pressure fuel pump at the high demand level and control the valve means to supply fuel from the high pressure fuel pump to the fuel accumulator.
As described above, in one example, the high demand level may be a maximum demand level of the high pressure fuel pump, wherein the maximum demand level selected to deliver a maximum flow of fuel from the high pressure fuel pump based on an engine speed. Furthermore, during a subsequent engine fuel demand event, the valve means may be controlled by the electronic controller to supply fuel from the accumulator to the engine and the high pressure fuel pump may be operated by the electronic controller at the low demand level during the period in which fuel is being supplied from the accumulator to the engine. The subsequent engine fuel demand event may be an event in which fuel is required by the engine to accelerate the motor vehicle while the low demand level may be a minimum demand level of the high pressure fuel pump. In addition, during the vehicle over-run event, the electronic controller may be further operable to reduce the demand level for the high pressure fuel pump from the high demand level to the low demand level if the accumulator is full. Further still, during the vehicle over-run event, the electronic controller may operate the high pressure fuel pump at the high demand level if the speed of the motor vehicle is above a predefined minimum vehicle speed and may operate the high pressure fuel pump at the low demand level if the speed of the motor vehicle is below the predefined minimum vehicle speed.
According to a third aspect of the present disclosure there is provided a motor vehicle having a fuel supply system constructed in accordance with said second aspect of the present disclosure just described. As one example, the motor vehicle may be a hybrid motor vehicle having at least one electrical traction motor to assist with driving of the motor vehicle and an electrical generator to recuperate energy from the motor vehicle and store it for subsequent use by the at least one electrical traction motor wherein, when the speed of the motor vehicle is above a predefined minimum vehicle speed during the vehicle over-run event, the fuel supply system is used to recuperate energy from the motor vehicle by storing fuel in the accumulator and simultaneously the electrical generator is used to recuperate energy from the motor vehicle and, when the speed of the motor vehicle is below the predefined minimum vehicle speed, the generator is used to recuperate energy from the motor vehicle and store it as electrical energy and the electronic controller operates the high pressure fuel pump at the low demand level. In one example, the traction motor and the generator may be integrated into a single electrical machine.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.